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Recently, III-V/c-Si heterojunction (c-Si HJ) tandem solar cells received considerable attention owing to their high conversion efficiency. In a tandem configuration, current matching has a significant impact on conversion efficiency. Specifically, in the two-terminal tandem structure, the sub-cell with the lowest current density (Jsc) dominates the Jsc of the tandem cell, which in turn, dominates the overall conversion efficiency of the tandem device. Meanwhile, in a four-terminal tandem structure, although the current matching condition is not mandatory, an efficient light distribution is necessary to achieve high efficiency in each sub-cell, which in turn results in a high efficiency of the tandem cell. Herein, we propose two- and four-terminal GaAs/c-Si HJ tandem solar cells using effective albedo reflections (RA) to overcome the aforementioned limitations. As RA increased, the current density of the c-Si HJ solar cells increased from 3.07 mA/cm2 (RA = 10%) to 39.90 mA/cm2 (RA = 100%) on the rear side of the cell, thereby, overcaming the existing current density limit. In addition, we investigated the tandem structures via simulation to provide a practical direction for achieving high efficiency. Finally, normalised outputs of 40.00% and 40.31% were achieved for the two-terminal and four-terminal GaAs/c-Si HJ bifacial tandem solar cells, respectively, with a real-life albedo from common ground surfaces, such as sand.

InGaN-based blue light-emitting diodes (LEDs), with their high efficiency and brightness, are entering the display industry. However, a significant gap remains between the expectation of highly efficient light sources and their experimental realization into tiny pixels for ultrahigh-density displays for augmented reality. Herein, we report using tailored ion implantation (TIIP) to fabricate highly efficient, electrically-driven pixelated InGaN micro-LEDs (μLEDs) at the mid-submicrometre scale (line/space of 0.5/0.5 μm), corresponding to 8,500 pixels per inch (ppi) (RGB). Creating a laterally confined non-radiative region around each pixel with a controlled amount of mobile vacancies, TIIP pixelation produces relatively invariant luminance, and high pixel distinctiveness, at submicrometre-sized pixels. Moreover, with the incomparable integration capability of TIIP pixelation due to its planar geometry, we demonstrate 2,000 ppi μLED displays with monolithically integrated thin-film transistor pixel circuits, and 5,000 ppi compatible core technologies. We expect that the demonstrated method will pave the way toward high-performance μLED displays for seamless augmented-reality glasses. Submicrometre-sized InGaN-based light-emitting diodes are fabricated by tailored ion implantation. The devices are free from electrical leakage and show a luminance of 7,440 nit at 4.9 A cm−2 even at the line/space scale of 0.5/0.5 μm (= 8,500 ppi).

In this study, technology computer-aided design (TCAD) was used to investigate carrier selective contact solar cell performance based on the boundary of tunneling oxide and electron selective contact layer properties. The role of tunneling oxide quality in the passivation and inter-diffusion properties of the plasma-enhanced chemical vapor deposition of phosphorus-doped amorphous silicon as an electron selective contact layer is studied for carrier selective contact solar cells. Tunnel oxide quality varies according to the ratio of Si4+ to Si2+ state. For the Si4+/Si2+ ratio of 4, open-circuit voltage of 730 mV and the lowest interface trap density of 5.3 × 1010 cm−2 eV−1 are achieved. The change in diffusion depth of the doped layer with respect to the annealing temperature is analysed by transmission electron microscopy (TEM)/energy dispersive X-ray spectroscopy (EDS) measurement. Carrier selective contact solar cell parameters are optimized by incorporating the experimental values of interface trap density, inter-diffused impurity concentration, and depth in the Quokka 3 TCAD tool. Solar cell conversion efficiency of 24.31% was obtained. To understand the response of carrier selective solar cell to the environmental changes, the output characteristics of the solar cell were studied by varying the illumination temperature by 10% of the standard test conditions (STC) and temperature from 277 K to 377 K (difference of 100 K).

We report the effects of the nitride passivation layer on the structural, electrical, and interfacial properties of Ge metal-oxide-semiconductor (MOS) devices with a hafnium oxide (HfO₂) gate dielectric layer deposited on p-type 〈100〉 Ge substrates. X-ray photoelectron spectroscopy analysis confirmed the chemical states and formation of HfO₂/Ge₃N₄ on Ge. The interfacial quality and thickness of the layers grown on Ge were confirmed by high-resolution transmission electron microscopy. In addition, the effects of post-deposition annealing (PDA) on the HfO₂/Ge₃N₄/Ge and HfO₂/Ge samples at 400 °C in an (FG+O₂) ambient atmosphere for 30 min were studied. After PDA, the HfO₂/Ge₃N₄/Ge MOS device showed a higher dielectric constant (k) of ~21.48 and accumulation capacitance of 1.2 nF, smaller equivalent oxide thickness (EOT) of 1.2 nm, and lower interface trap density (Dit) of 4.9×1011 cm-2 eV-1 and oxide charges (Qeff) of 7.8×1012 cm-2 than the non-annealed sample. The I-V analysis showed that the gate leakage current density of the HfO₂/Ge₃N₄/Ge sample (0.3-1 nA cm-2 at Vg = 1 V) was half of that of the HfO₂/Ge sample. Moreover, the barrier heights of the samples were extracted from the Fowler-Nordheim plots. These results indicated that nitride passivation is crucial to improving the structural, interfacial, and electrical properties of Ge-based MOS devices.

A novel approach involving CO2 plasma treatment of intrinsic hydrogenated amorphous silicon was developed to form ultrathin silicon oxide (SiOx) layers, that is, passivated tunneling layers (PTLs), for the fabrication of passivated tunneling contacts. These contacts were formed by depositing the PTL/n-type hydrogenated nanocrystalline layer (nc-Si:H(n))/c-Si(n) stacks. The results indicated that a higher CO2 plasma treatment pressure was preferred for the formation of oxygen-richer components in the silicon oxide films, with Si2+, Si3+, and Si4+ peaks, and a smoother PTL/c-Si heterointerface. The PTLs with higher oxidation states and lower surface roughness exhibited advantages for the c-Si surface passivation, with a maximum implied open-circuit voltage of approximately 743 mV. The lowest contact resistivity of approximately 60 mΩ cm2 was obtained using nc-Si:H(n)/PTL/c-Si(n) as the passivated tunneling contact. Most importantly, the in situ process can help prevent the contamination of the heterointerfa...

Substrate temperature has an important role on the characteristic properties of a plasma deposited thin film silicon. In a heterojuction (HJ) solar cell, the higher deposition temperature initiates unwanted thermal diffusion of atom from one layer to another, thereby degrading device characteristics. Hence, we investigated the effect of substrate temperatures (Ts) on p-type material and HJ device characteristics. We prepared p-type nanocrystalline silicon oxide (p-nc-SiO:H) layer at different Ts, varying from 170 °C to 80 °C and observed that its opto-electronic properties improve at a lower Ts. These p-nc-SiO:H were used in HJ solar cell as emitter and we found that the film prepared at 80 °C gives the best result. This emitter layer shows wide optical gap (2.32 eV), high electrical conductivity (3.5 S/cm) and high crystallinity (44%). In the rear emitter HJ solar cells, an improvement in fill factor from 72.2% to 74.5%, open circuit voltage from 708 mV to 718 mV and power conversion efficiency (PCE) from 19.3% to 20.1% was observed when the emitter of the cells was prepared at 170 °C–80 °C.

Effects of post deposition annealing (PDA) atmosphere, including oxygen (O2) gas and forming gas (FG), on interfacial and electrical properties of a HfO2 gate dielectric on nitrided Ge are analyzed. Experiments to study the dielectric morphology, interface quality, and chemical composition of HfO2/Ge3N4/Ge devices were carried out using X-ray diffraction, high-resolution transmission electron microscopy (HRTEM) imaging, and X-ray photoelectron spectroscopy (XPS) measurements, respectively. The XPS study confirmed that O2 PDA effectively improves the HfO2 film stoichiometry, and the stability of the interface between HfO2/Ge3N4/Ge stacks is enhanced. Further, HRTEM images showed that the interface between HfO2/Ge3N4/Ge stacks for O2-annealed devices was smooth, uniform, and flat. The experimental results for devices annealed in O2 at 500 °C exhibited improved interfacial and electrical characteristics, such as a high dielectric constant of ~19.50; high capacitance, 1.24 nF, low equivalent oxide thickness, 1.74 nm; interface trap density, 2.18 × 1011 cm−2 eV−1; oxide charges, 2.50 × 1012 cm−2; and gate leakage currents in the order nA of 0.5 × 10−9 A/cm2, as compared with FG annealing devices. The Fowler−Nordheim tunneling current conduction mechanism was also verified. Therefore, these results are evidence that the O2 PDA process improves the interfacial and electrical properties of HfO2/Ge3N4/Ge metal-oxide-semiconductor (MOS) devices as compared with FG annealing, which is important for future Ge-based complementary MOS device performance and reliability.

A tunnel recombination junction (TRJ) layer for hydrogenated amorphous silicon (a-Si:H)/ Cu(In,Ga)Se₂ (CIGS) tandem solar cells is investigated. An Al-doped zinc oxide (AZO) thin film is applied to the TRJ, and the influence of electron beam (e-beam) irradiation on defects along the TRJ is investigated. The AZO thin films are prepared using radio frequency (RF) sputtering and the e-beam is irradiated at 200 W RF power and 2 keV DC power for 5 min. In the e-beam irradiated AZO thin film, the number of oxygen vacancies and Zn interstitials increases, which in turn strengthens the effect of defect-enhanced tunnel recombination.

Effective carrier contact with excellent surface passivation is essential for archiving high efficiency silicon solar cells. In this study, optical, passivation and stoichiometric characteristics of MoOx thin films were analyzed by varying thickness, temperature and ambient annealing. The 10 nm thick MoOx films showed high optical transmittance (89.81%) in the visible near infra-red (NIR) wavelength (380–1100) nm region and wide optical bandgap of 3.25 eV. An improved minority carrier lifetime of 2.24 ms was recorded for O2 ambient at 130 °C due to less additional defects in the MoOx films. X-rays photoelectron spectroscopic analysis confirmed that O2 ambient annealing greatly influenced the MoOx stoichiometric and reduce the formation defective state densities at the Fermi energy initiating from the tail of an oxygen vacancy and inducted the defect band within the energy bandgap. Carrier selective contact (CSC) solar cells were fabricated by using 10 nm thick MoOx film as hole extraction layer exhibited the high performance as; open circuit voltage (Voc) = 708 mV, current density (Jsc) = 37.80 mA/cm2, fill factor (FF) = 74.95% and efficiency (η) = 20.06%. These results implies that the MoOx is an important material to use in future CSC solar cell applications with the concept of new advantages such as dopant free, non-toxic and low temperature fabrication process.

Transition metal oxides (TMO) are extensively applied as a surface passivation and carrier-selective contact layer through replacing boron/phosphorus doped emitter layers in silicon heterojunction (SHJ) solar cell applications. In this regard, molybdenum oxide (MoO3) has drawn a significant attention as a hole extraction layer owing properties such as wide bandgap (∼3 eV), high work function (>6 eV) and low temperature deposition. Thus, we fabricated SHJ solar cells with a dopant-free MoOx applied at the front surface contact layer. Thermally evaporated MoOx films were exhibited optical characteristics such as high transmittance, high bandgap and low absorption coefficient as compared to a-Si:H(p) and μc-SiOx:H (p) layers. X-ray photoelectron spectroscopy (XPS) analysis confirmed the stoichiometric and oxidation deficiency states of the of the MoOx layers. Whereas, MoOx films undergoing long-term air exposure showed an increase in Mo5+ cations due to the increased oxygen vacancy. The fabricated MoOx/c-Si heterojunction solar cells achieved a significant power conversion efficiency (η) of 20%, best open circuit voltage (Voc) of 695 mV, high short circuit current density (Jsc) of 38.88 mA/cm2 and a fill factor (FF) of 74.0%. These results implying that MoOx is as an excellent dopant-free material for alternate p-doped a-Si:H emitter layers in SHJ solar cell applications.

Boron doped hydrogenated silicon films used as thermo-sensing layers in infrared detectors or uncooled micro-bolometers are prepared by radio-frequency plasma-enhanced chemical vapor deposition (PECVD). In this work, we investigated TCR (higher the better) and sheet resistance, Rsheet (lower the better), which are important factors for thermos-sensing layer used in uncooled microbolometer. The crystalline volume fraction (Xc) of films is controlled to get silicon films that satisfy the characteristics of high TCR and low Rsheet. Through the control, amorphous, mixed- and microcrystalline phases were identified. As a result, the best TCR and Rsheet were obtained in the mixed-phase. For the films, TRC is around 1–3%/K, Rsheet is around 3–61.4 MΩ/□ and Xc is around 7–17%. The 1/f noise is measured for various phases. It is found that 1/f noise of boron doped hydrogenated mixed-phase silicon (BMP-Si:H) is smaller than that of the amorphous phase. The results of BMP-Si:H films show that they are more suitable as thermos-sensing layers than boron doped hydrogenated amorphous silicon films.

In this study, the contact mechanism between Ag&ndash, Al and Si and the change in contact resistance (Rc) were analyzed by varying the firing profile. The front electrode of an n-type c-Si solar cell was formed through a screen-printing process using Ag&ndash, Al paste. Rc was measured by varying the belt speed and peak temperature of the fast-firing furnace. Rc value of 6.98 m&Omega, cm&minus, 2 was obtained for an optimal fast-firing profile with 865 &deg, C peak temperature and 110 inches per min belt speed. The contact phenomenon and the influence of impurities between the front-electrode&ndash, Si interface and firing conditions were analyzed through scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The EDS analysis revealed that the peak firing temperature at 865 &deg, C exhibited a low atomic weight percentage of Al (0.72 and 0.36%) because Al was involved in the formation of alloy of Si with the front electrode. Based on the optimal results, a solar cell with a conversion efficiency of 19.46% was obtained.

In this paper, the relationship between coordination complexes and electrical properties according to the bonding structure of boron and silicon was analyzed to optimize the p–n junction quality for high-efficiency n-type crystalline solar cells. The p+ emitter layer was formed using boron tribromide (BBr3). The etch-back process was carried out with HF-HNO3-CH3COOH solution to vary the sheet resistance (Rsheet). The correlation between boron–silicon bonding in coordination complexes and electrical properties according to the Rsheet was analyzed. Changes in the boron coordination complex and boron–oxygen (B–O) bonding in the p+ diffused layer were measured through X-ray photoelectron spectroscopy (XPS). The correlation between electrical properties, such as minority carrier lifetime (τeff), implied open-circuit voltage (iVoc) and saturation current density (J0), according to the change in element bonding, was analyzed. For the interstitial defect, the boron ratio was over 1.8 and the iVoc exceeded 660 mV. Additional gains of 670 and 680 mV were obtained for the passivation layer AlOx/SiNx stack and SiO2/SiNx stack, respectively. The blue response of the optimized p+ was analyzed through spectral response measurements. The optimized solar cell parameters were incorporated into the TCAD tool, and the loss analysis was studied by varying the key parameters to improve the conversion efficiency over 23%.

Excellent surface passivation and carrier selective contact formed by the metal oxide induced junctions is required for future high efficiency silicon solar cells. Due to wide optical bandgap and high work function of molybdenum oxide (MoOx, x

In this work, we investigate numerical simulations of single junction hydrogenated amorphous silicon solar cells (a-Si:H), Cu (In, Ga) Se2 (CIGS) solar cells, and tandem solar cells with a-Si:H as the top cell and (CIGS) as the bottom cell using an advanced semiconductor analysis program. The optical bandgaps and thicknesses of the tandem solar cell were studied to optimize current matching. The tunnel-recombinaton (TJ) junctions were studied with different structures. The optimal structure was investigated using the optimal TJ junction, which consists of p-type microcrystalline silicon, n-type nanocrystalline silicon and AZO. The characteristics of the optimal a-Si:H/CIGS solar cell were a short circuit current density of 17.57 mA/cm2, and an open circuit voltage of 1.67 V. These results can be used as a basis for effectively developing low-cost and high-efficiency solar cells.

We report an efficient light trapping for maskless large area randomly textured glass structures with various haze ratios in silicon thin film solar cells. By well controlling the ratio of buffered hydrofluric acid (BHF) and sulfuric acid (H2SO4), we were able to prepare the randomly textured maskless glass structures with high transmittance above 90% and variable haze ratio from 20.79 to 54.78% in the visible wavelength (380–800 nm) region. It was observed that haze ratio of textured glass was dependent on feature size, etching depth and rms roughness. Multi-textured aluminum-doped zinc oxide (AZO) films were deposited on textured glass structures showed high transmittance (83.78–85.06)% and haze ratio (45.03–65.05)% in visible wavelength region. An enhancement in haze ratio of multi-textured AZO films was due to an increase of rms roughness from 16.4 to 185.5 nm as shown by 3D-alpha step profiler images. Multi-textured AZO films deposited on various textured glass superstrates were employed as a front transparent conductive oxide (TCO) layer for the fabrication of amorphous silicon (a-Si) thin film solar cells (TFSCs). The a-Si TFSCs deposited on structure-C glass showed the maximum performance as; open circuit voltage = 869 mV, short circuit current density = 16.68 mA/cm2, fill factor = 67.8% and efficiency = 9.79%. An enhancement of photocurrent was noticed from 15.64 to 16.68 mA/cm2 for as deposited a-Si TFSCs to structure-C based a-Si TFSCs.

We optimized hydrogenated amorphous silicon oxide (a-SiOx:H) as a buffer layer at the p/i interface of hydrogenated amorphous silicon germanium (a-SiGe:H) solar cells. This buffer layer was intended to effectively diminish the band discontinuity between the high-bandgap p-window layer and low-gap a-SiGe:H absorption layer, thereby enhancing the cell performance. The open-circuit voltage (Voc) increased by 3.7% as the [CO2]/[SiH4] gas ratio increased from 0 to 0.06. In addition, the short-circuit current density (Jsc) gradually increased with the gas ratio. Using the optimized a-SiOx:H buffer layer, a high performance of 9.6% was recorded for narrow-gap a-SiGe:H thin film solar cells. a-SiGe:H solar cells with optimized a-SiOx:H buffer layers, used as middle subcells, are expected to enhance the total Voc of triple-junction configuration solar cells.

We report the light scattering characteristics of multi-textured aluminum-doped zinc oxide (AZO) thin films with high optical transmittance, haze ratio and step coverage for amorphous silicon thin film solar cells (a-Si TFSCs). Multi-textured AZO films were deposited on inverted hemisphere textured (IHT) glass surface morphologies. Multi-textured process was used to create modulated surface morphologies with micro and nano-features useful for the light scattering in visible as well as near-infrared wavelength region. Highly transparent IHT glass surface morphologies with high haze ratio were prepared by wet chemical etching of periodic glass substrates. Total transmittance of the IHT glass substrates showed higher average values (91.38–93.40%) as compared to that of bare glass (90.94%) in the visible wavelength region due to lower reflectance. Multi-textured AZO films showed higher rms roughness 100.479 nm, optical transmittance 82.60% and haze ratio 75.09% in the visible wavelength region. X-ray photoelectron spectroscopic analysis of multi-textured AZO thin films was used to study the atomic compositions and chemical binding states. Multi-textured AZO films with high transmittance and haze ratio were used as front transparent conductive oxide layers for the fabrication of a-Si TFSCs using an absorber layer thickness of 400 nm. Multi-textured AZO films deposited on the optimal textured glass surface morphologies yield the maximum performance of a-Si TFSCs as; Voc = 871 mV, Jsc = 16.55 mA/cm2, FF = 66.6% and η = 9.61%. An enhancement of photocurrent was noticed from 15.64 to 16.55 mA/cm2 for the a-Si TFSCs deposited on as deposit AZO to optimal textured AZO films.

In this paper, we report a technical approach regarding an amorphous silicon (a-Si)/crystalline silicon (c-Si) heterojunction solar cell to solve the previous issues, and we investigate the applications of front and back transparent conductive oxides (TCOs) on this high-efficiency solar cell. The presentation of front and rear-emitter structure solar cells is included, and we investigate the TCO-material candidates for the Si heterojunction (SHJ) solar cell according to the electrical and optical properties. A high-quality TCO film is very important because it is linked to the efficiency of the c-Si-based silicon solar cell. The intention here is the applying of a high-efficiency SHJ solar cell by fabricating the high-quality TCO materials of the investigation of this study.

Silicon materials have been widely used as thermo-sensing layers in infrared detectors or uncooled micro-bolometers. Parameters such as a large thermal coefficient of resistance (TCR), low sheet resistance (Rs), and low 1/f noise are important for high performance of these devices. However, there is always a trade-off between these parameters. For example, the crystalline silicon materials typically exhibit low Rs and 1/f noise, and significantly low TCR, while the amorphous silicon materials generally have large TCR, and considerably high Rs and 1/f noise. Consequently, the best trade-off can be achieved by using a mixed-phase structure of silicon materials, i.e. an intermediate form between the crystalline and amorphous structures. Herein we report the important characteristics of hydrogenated mixed-phase silicon films, deposited by the plasma-enhanced chemical vapour deposition process, for infrared detectors. The films in the mixed-phase structure showed high TCR values in the range of 2–3% K–1 and moderate sheet resistances in range of 10–40 MΩ sq−1. These results indicate that the mixed-phase silicon films are potential alternatives to conventional boron doped hydrogenated amorphous and microcrystalline silicon films for use as thermo-sensing layers in infrared detectors.

Molybdenum oxide (MoOx), owing to its large work function, is an attractive material for hole-selective contact (HSC) in crystalline Si-based solar cells because it introduces upward band bending when constructed into a heterojunction silicon (SHJ) cell structure. In this study, we fabricated a p-type SHJ bifacial solar cell with a rear-side MoOx HSC layer. The MoOx thickness was varied from 3 to 15 nm, and cell bifaciality was addressed. The cell efficiency decreased when the MoOx thickness was increased to more than 5 nm. A maximum front-side cell efficiency of 17.89% was obtained, while the rear efficiency was 16.02%, which shows the potential of MoOx for p-type bifacial cell fabrication. The maximum open circuit voltage (VOC) and short circuit current density (JSC) for the front side were 635.71 mV and 35.57 mA/cm2, respectively, while the rear side VOC and JSC were 623.62 mV and 32.67 mA/cm2, respectively. The interfacial properties were carefully studied as a function of MoOx thickness. This work demonstrates the importance of selecting MoOx for p-type crystalline silicon (c-Si) solar cells.

We examined different buffer layers at the i/n interface of narrow-gap amorphous silicon germanium alloy (a-SiGe:H)-based thin-film solar cells. These buffers included a conventional hydrogenated amorphous silicon (a-Si:H), an inversely graded hydrogenated amorphous silicon germanium, and a crystalline seed buffer (CSB). The solar cell with the CSB shows the highest performance, of 10%. The better carrier extraction at the rear side of the device is attributed to the role of the CSB layer. The effect of CSB thickness from 50 nm to 100 nm on cell performance was examined. Cell efficiency increased with the buffer thickness up to 80 nm and decreased with buffer thickness of 100 nm. This decrease can be attributed to increased defect densities of the buffer due to less efficient passivation of amorphous phase at the crystalline column boundaries.

Tandem-structured amorphous Si solar cells can absorb a broader range of solar spectra than a single-junction device. In a tandem cell, usually a thicker bottom subcell becomes necessary to absorb the required number of photons from long-wavelength light to generate the desired current density. Alternatively, an optoelectronically improved active layer and light-trapping scheme can also be used with a thinner bottom subcell. In this respect, we investigated bottom subcell of tandem solar cells with microcrystalline Si active layer. Three of the primary parameters that were progressively varied for the bottom subcells were the crystalline volume fraction (X c ) of the active layer, buffer layer at the i/n interface, and back reflector (BR). Here, the buffer layer and higher X c are expected to improve respectively the electronic properties of the i/n interface and the active layer of the bottom subcell. Furthermore, a suitable BR can reflect the unabsorbed long-wavelength light back to the cell for further absorption; thereby raising its current density. We have observed that low-power deposition of the microcrystalline Si active layer (150 W), an 8 nm thick buffer layer at the i/n interface, and a zinc oxide BR layer gave best results in a tandem solar cell. An optimized tandem cell exhibited an open-circuit voltage, short-circuit current density, fill factor, and efficiency of 1.445 V, 12.32 mA/cm 2 , 71.56%, and 12.74%, respectively.

Wide band gap and highly conducting n-type nano-crystalline silicon film can have multiple roles in thin film solar cell. We prepared phosphorus doped micro-crystalline silicon oxide films (n-μc-SiO:H) of varying crystalline volume fraction (Xc) and applied some of the selected films in device fabrication, so that it plays the roles of n-layer and back reflector in p-i-n type solar cells. It is generally understood that a higher hydrogen dilution is needed to prepare micro-crystalline silicon, but in case of the n-μc-SiO:H an optimized hydrogen dilution was found suitable for higher Xc. Observed Xc of these films mostly decreased with increased plasma power (for pressure 0.08 sccm. In order to determine deposition conditions for optimized opto-electronic and structural characteristics of the n-μc-SiO:H film, the gas flow rates, plasma power, deposition pressure and substrate temperature were varied. In these films, the Xc, dark conductivity (σd) and activation energy (Ea) remained within the range of 0–50%, 3.5×10−10 S/cm to 9.1 S/cm and 0.71 eV to 0.02 eV, respectively. Low power (30 W) and optimized flow rates of H2 (500 sccm), CO2 (5 sccm), PH3 (0.08 sccm) showed the best properties of the n-μc-SiO:H layers and an improved performance of a solar cell. The photovoltaic parameters of one of the cells were as follows, open circuit voltage (Voc), short circuit current density (Jsc), fill-factor (FF), and photovoltaic conversion efficiency (η) were 950 mV, 15 mA/cm2, 64.5% and 9.2% respectively.

Separate influences of a hydrogenated amorphous silicon (a-Si:H) buffer layer at the p/i interface and staircase band gap profiling of entire absorption layer on cell parameters, such as open-circuit voltage (Voc), short-circuit current density (Jsc) and fill factor (FF), of hydrogenated amorphous silicon germanium (a-SiGe:H) thin film solar cells are discussed. An added thin a-Si:H buffer layer at the p/i interface can mainly improve Voc and Jsc while the staircase band gap profiling can enhance FF. Consequently, a combination of the buffer layer and band gap profiling can lead to significantly enhance Voc, Jsc and especially FF. A significant performance-improvement of the a-SiGe:H solar cell from 8.3% up to 9.8% was recorded by this combination. Role of the buffer layer and band gap profiling process was examined by empirical results and simulations.

Single junction solar cells were fabricated with intrinsic hydrogenated amorphous silicon germanium (a-SiGe:H) as the active layer, that shows a 10% photovoltaic conversion efficiency. The a-SiGe:H active layer of the solar cells of type-A had constant band gap materials while that of type-B had a four step graded band gap by composition gradient (CG). The cells with composition gradient show an enhancement in fill factor and open circuit voltage (V oc) by 5% and 20 mV respectively, with respect to a cell without the graded band gap active layer. Such an enhanced device performance is attributed to reduction in recombination loss of photo-generated electron hole pairs. The effect of this photo-current loss was investigated in the electrical bias dependent external quantum efficiencies (EQE), illumination dependent current-voltage measurements and dark current-voltage characteristics. The device parameters like reverse saturation current density (J o), series resistance (R s) and diode quality factor (n) were also estimated. In comparison to the cell without the composition gradient, the EQE shows a reduced recombination loss across the whole wavelength range for the cell with the CG. Furthermore, the introduction of the CG results in a significantly increased shunt resistance from 720 to 1200 Ω.cm 2. The estimated n values of the cells under dark operating condition, decreases from 1.8 to 1.7 along with J o from 3 × 10 −7 down to 4.5 × 10 −8 A/cm 2 with CG, while the same parameters decreased from 3.73 to 3.06, 2.96 × 10 −6 to 3.05 × 10 −7 A/cm 2 respectively under AM1.5G insolation.

Rho-associated protein kinases (ROCKs) have various cellular functions, which include actin cytoskeleton remodeling and vesicular trafficking, and there are two major mammalian ROCK isotypes, namely, ROCK1 (ROKβ) and ROCK2 (ROKα). The ROCK2-specific inhibitor KD025 (SLx-2119) is currently undergoing phase II clinical trials, but its cellular functions have not been fully explored. In this study, we investigated the functions of KD025 at the genomics level by bioinformatics analysis using the GSE8686 microarray dataset from the NCBI GEO database, in three different primary human cell lines. An initial microarray analysis conducted by Boerma et al. focused on the effects of KD025 on cell adhesion and blood coagulation, but did not provide comprehensive information on the functions of KD025. Our analysis of differentially expressed genes (DEGs) showed ~70% coincidence with Boerma et al.’s findings, and newly identified that CCND1, CXCL2, NT5E, and SMOX were differentially expressed by KD025. However, due to low numbers of co-regulated DEGs, we were unable to extract the functions of KD025 with significance. To overcome this limitation, we used gene set enrichment analysis (GSEA) and the heatmap hierarchical clustering method. We confirmed KD025 regulated inflammation and adipogenesis pathways, as previously reported experimentally. In addition, we found KD025 has novel regulatory functions on various pathways, including oxidative phosphorylation, WNT signaling, angiogenesis, and KRAS signaling. Further studies are required to systematically characterize these newly identified functions of KD025.

We report the effects of the nitride passivation layer on the structural, electrical, and interfacial properties of Ge metal-oxide-semiconductor (MOS) devices with a hafnium oxide (HfO₂) gate dielectric layer deposited on

Thin-film silicon solar cells are promising candidates for the low-cost production of electricity from sunlight. However, their efficiency remains relatively low, which is one of the major issues for their commercialisation. In the thin-film silicon technology, light trapping is an important design consideration for achieving a higher device efficiency. An advanced light-trapping technology is expected to boost the efficiency of solar cells further. Therefore, we investigated the development of an advanced light-trapping scheme in a two-dimensional periodic surface structure produced via inductively coupled plasma reactive-ion etching. The texture of the glass surface was varied under various plasma conditions. For the various shapes and sizes of the obtained surface texture, the increased height and base angle of the individual texture showed an overall increase in the diffused transmission of light. In some cases, the diffused transmission was as high as 89 % of the total light transmitted through the glass. The effect of the textured glass on a solar cell was investigated through simulation. Results show that the efficiency of a single-junction solar cell can be enhanced significantly when such a textured glass is used instead of a non-textured glass.

Herein, a single-junction GaAs solar cell using a wide-gap n-type doped ZnO layer as a front electron-selective contact is proposed. An atomic layer deposition approach was used to deposit a thin ZnO layer on a GaAs substrate, which demonstrated excellent surface passivation properties by significantly reducing the native oxide statuses of the Ga–O and As–O bonds at the GaAs surface. Additionally, n-type doped ZnO layer acted as a front electron-selective contact layer that blocked hole transport and promoted electron collection at the front side. A wide-gap ZnO window layer was shown to enhance cell absorption in the short wavelength range and increase built-in potential, and was proven to be a suitable alternative to the conventional AlGaAs front window layers used in highly efficient single-junction GaAs cells.

We investigated solar cells with graded band gap hydrogenated amorphous silicon germanium active layer and hydrogenated microcrystalline silicon buffer layer at the interface of intrinsic and n-type doped layer. A significantly improved, 10.4% device efficiency was observed in this type of single junction solar cell. The intrinsic type microcrystalline silicon buffer layer is thought to play dual roles in the device; as a crystalline seed-layer for growth of n-type hydrogenated microcrystalline silicon layer and helping efficient electron collection across the i/n interface. Based on these, an enhancement in cell parameters such as the open-circuit voltage (Voc), and fill factor (FF) was observed, where the FF and Voc reaches up to 69% and 0.85 V respectively. Our investigation shows a simple way to improve device performance with narrow-gap silicon germanium active layer in solar cells in comparison to the conventionally constant band gap device structure.

In this article we present a mechanism for creating metastable defects in intrinsic hydrogenated amorphous silicon (a-Si:H) layers by changing the flow-rate ratio of SiH4 and H2. This is an important cardinal property that restricts the performance of both solar cells and thin-film transistors (TFT). Light or electrical bias results in generation of metastable dangling bonds. We evaluated the gas flow-rate ratio dependence of current decrease before and after application of electrical bias stress. Furthermore, we produced an a-Si:H TFT for comparison with a single-layer a-Si:H. Intrinsic layers deposited by SiH4 to H2 flow-rate ratios of 1:3 exhibited greater resistance to stress. In a-Si:H single layer experiment, we got a similar result, samples with SiH4 and H2 flow-rate ratios of 1:3 exhibited less decrease in current after application of electrical bias stress. These results will facilitate fabrication of more-stable a- Si:H thin film p-i-n solar cells.